docs: def tooltip_ellipsis(source, length=0):
      ''' return the plain text representation of markdown encoded text.  That
      is the texted without any html tags.  If ``length`` is 0 then it
      will not be truncated.'''
      try:
          length = int(length)
      except ValueError:  # invalid literal for int()
          return source  # Fail silently.
      ellipsis = '<a href v-tooltip title="{0}">...</a>'.format(source)
      return Markup((source[:length] + ellipsis)
                    if len(source) > length and length > 0 else source)